Installing drivers for Windows is simply a matter of inserting your Snow Leopard install DVD after Windows 7 is installed. Drivers will automatically be installed. The Boot Camp 3.1 update does the same thing but must be downloaded and run from within Windows 7.

Why are you worring about drivers being installed for hardware you don't have? The Windows installer knows which to install for what type of hardware you have; be it an nVidia or ATI GPU. Inactive drivers take up little space and are stored in your windows folder\system32\drivers.

Just insert your Snow Leopard DVD while Windows 7 is running, go to "My Computer" and double click "setup.exe". Drivers will be reinstalled. Afterward, go to the Apple site and download Boot Camp 3.1 and run the installation from Windows 7. Make sure you download the correct version for your Windows 7, either 32 bit or 64 bit.